The invention relates to a bunged vessel of thermoplastic synthetic material having a central cylindrical section, opposite end surfaces and a carriage and transport ring located on the shell of the vessel adjacent at least one of the head and bottom surfaces. The transport ring is generally solid in cross-section and includes horizontal and vertical bearing surfaces for the arm of a vessel lifter to be used in transporting the vessel. The transport ring is typically formed as one piece with the shell of vessel and joined thereto by a connecting web. The connection web extends generally axially of the vessel from its outer cylindrical wall section toward the associated end surface of the vessel. The shell of the vessel also includes a conical section extending from the cylindrical section toward the head and bottom end surfaces of the vessel. The connecting web for the transport ring and the conical section of the shell of the vessel produce an annular groove therebetween.
The vessel may be a bunged vessel which is produced entirely in the blow molding process and wherein the carriage and transport rings are formed as one piece with the shell of the vessel. However, likewise known are bunged vessels wherein the cylindrical section of the shell of the vessel and the end sections of the vessel are manufactured separately from one another. End section manufactured in the injection molding process, with the carriage and transport rings situated thereon, are then welded onto the cylindrical section of the vessel in an additional operation.
Ordinarily, according to DE-GM 7,600,621 such carriage and transport rings have a cross-section with a horizontal and vertical web. The free end of the vertical web is directed towards the respective end of the vessel and the horizontal web is formed radially outward in the shell of the vessel. Because control in the critical weld-seam region of the vessel was difficult in this embodiment, the carriage and transport ring was designed so that the critical weld zones created during the molding operation are largely relieved of bending forces. With this construction, the ring, upon impact stress, elastically deforms in the peripheral direction and hence relative to the shell of the vessel. To provide for this, the attachment of the carriage and transport ring to the shell of the vessel is designed as a flexible attachment. To this end, the carriage and transport ring was connected with the vessel by an annular connecting web merging with the shell of the vessel and adjoining the horizontal bearing surface.
The annular connecting web is stressed only by harmless tensile loads which are introduced into the shell of the vessel upon lifting transporting the vessel in the vessel lifter.
In prior constructions, the annular connecting web of the carriage and transport ring merges with the shell of the vessel at a sharp angle to the axis of the vessel. This defines a groove between the carriage and transport ring and the adjacent shell part which rises conically. For reasons of providing an attachment of the ring to the shell which is as elastic as possible, the bottom of the groove terminates at the level of the horizontal bearing surface of the ring. The space between this bearing surface and the conical portion of the shell of the vessel should be very narrow in order that the stacking forces which are produced when another filled vessel is stacked on the head surface of the vessel are transmitted through the conical area of the shell directly into the rest of the shell of the vessel. U.S. Pat. No. 4,674,648 discloses such a construction. Such narrowing of this space impeded the use of a vessel lifter, which must for this reason be given a special shape.